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OpenCms is an enterprise-ready, easy to use website content management system based on Java and XML technology. Offering a complete set of features, OpenCms helps content managers worldwide to create and maintain beautiful websites fast and efficiently.

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/*
 * This library is part of OpenCms -
 * the Open Source Content Management System
 *
 * Copyright (c) Alkacon Software GmbH & Co. KG (http://www.alkacon.com)
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * For further information about Alkacon Software, please see the
 * company website: http://www.alkacon.com
 *
 * For further information about OpenCms, please see the
 * project website: http://www.opencms.org
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package org.opencms.ugc;

/**
 * A queue used to enforce a certain wait time between requests for sessions for the same form configuration.

*/ public class CmsUgcSessionQueue { /** True if the session queue is enabled. */ private boolean m_enabled; /** The wait time between multiple session requests for the same configuration. */ private long m_interval; /** The maximum number of threads waiting in the queue for the same configuration. */ private int m_maxLength; /** The time at which the next thread should be scheduled to run. */ private long m_nextScheduleTime; /** The number of threads waiting on this queue. */ private int m_waitCount; /** * Creates a new instance.

* * @param enabled true if the queue should be enabled * @param interval the wait time to use between multiple session requests * @param maxLength the maximum length of the queue */ public CmsUgcSessionQueue(boolean enabled, long interval, int maxLength) { m_enabled = enabled; m_interval = interval; m_maxLength = maxLength; if (interval < 0) { throw new IllegalArgumentException("Queue wait time must not be < 0"); } if (maxLength < 0) { throw new IllegalArgumentException("Queue maximum length must not be < 0"); } } /** * Creates a session queue based on the given configuration.

* * @param config the configuration for which to create the session queue * @return the newly created session queue */ public static CmsUgcSessionQueue createQueue(CmsUgcConfiguration config) { CmsUgcSessionQueue queue = new CmsUgcSessionQueue( config.needsQueue(), config.getQueueInterval().isPresent() ? config.getQueueInterval().get().longValue() : 0, config.getMaxQueueLength().isPresent() ? config.getMaxQueueLength().get().intValue() : Integer.MAX_VALUE); return queue; } /** * Updates the queue parameters from the configuration object.

* * @param config the form configuration */ public synchronized void updateFromConfiguration(CmsUgcConfiguration config) { m_enabled = config.needsQueue(); m_interval = config.getQueueInterval().isPresent() ? config.getQueueInterval().get().longValue() : 0; m_maxLength = config.getMaxQueueLength().isPresent() ? config.getMaxQueueLength().get().intValue() : Integer.MAX_VALUE; } /** * If there are currently any threads waiting on this queue, wait for the interval given on construction after the currenly last thread stops waiting.

* * @return false if the queue was too long to wait, true otherwise */ public synchronized boolean waitForSlot() { if (!m_enabled) { return true; } else { long now = System.currentTimeMillis(); long timeToWait = m_nextScheduleTime - now; if (timeToWait <= 0) { // This happens either if this method is called for the first time, // or if the wait interval for the last thread to enter the queue has // already fully elapsed m_nextScheduleTime = now + m_interval; return true; } else if (m_waitCount >= m_maxLength) { return false; } else { m_nextScheduleTime = m_nextScheduleTime + m_interval; m_waitCount += 1; try { // use wait here instead of sleep because it releases the object monitor // note that timeToWait can't be 0 here, because this case is handled in the first if() branch, // so wait() always returns after the given period wait(timeToWait); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } m_waitCount -= 1; return true; } } } }





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